Fixing threads: tap or die?

[buckjay]

I have a barrel ADCO cut and threaded which won't let me tighten a SureFire brake by hand (the A2 it came with threads on by hand). The brake is brand new, so there's no carbon build up to clean off.

What are my options? Do I get a tap and tap the brake or do I buy a die and try chase the threads on the barrel?

[mvician]

I would do both.

[Ryno12]

I would do both.

^^^ This, unless it's blatantly obvious which threads are bad.

I'm assuming the thread pitch is the same.

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[eodinert]

I would chase the threads on the muzzle attachment, and see if that worked, before I did anything to Adco's work. They are usually squared away.

[T2C]

I would square the threads on the muzzle attachment and not touch the barrel unless I had to. Think of it this way. A barrel will cost you a whole lot more to replace than a muzzle attachment if Mr. Murphy shows up to help while you are working on your rifle.

[Ryno12]

A barrel will cost you a whole lot more to replace than a muzzle attachment if Mr. Murphy shows up to help while you are working on your rifle.

:D True!

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[patrick sweeney]

Do you have another barrel? Does the muzzle device hand-turn onto a barrel that came already threaded?

Will this muzzle device be on this barrel until the barrel is done? Or will you be installing it on another barrel later?

Without the threading equivalent of go/no-go gauges, which is slightly off doesn't really matter, what matters is what you expect of your equipment.

Me, I'd try the muzzle device on another barrel. If it hand-turns easily on the other barrel, then chase the first barrels threads. If it doesn't, then tap the device threads.

[markm]

Yeah... there's something jookie going on...

I've put on a ton of mounts.. including some surefire.. and I've never seen something that'd thread the A2 but not the replacement. :confused:

[nova3930]

First I would invest $10 in a thread pitch guage and make double sure the threads are the same. Nothing says the guy doing the threading work didn't pick up the wrong tap or have the lathe set incorrectly.

Then, assuming they are the same thread pitch, I'd start looking at chasing the surefire with a tap. Since the A2 threads by hand that makes me think the surefire might have a burr in the threads, a rolled thread or something along those lines, again assuming the same thread pitch

ETA

Looking at surefires site, I see at least 4 different thread sizes on their various brakes, 2 UTS and 2 metric. Looks like the potential cutting the wrong threads to me.

[munch520]

Yeah... there's something jookie going on...

I've put on a ton of mounts.. including some surefire.. and I've never seen something that'd thread the A2 but not the replacement. :confused:

x2 this is confusing..

[buckjay]

Yeah... there's something jookie going on...

I've put on a ton of mounts.. including some surefire.. and I've never seen something that'd thread the A2 but not the replacement. :confused:

I'm not sure how many a ton of mounts is, but I've installed over 100 and I've had quite a few issues with tolerances. I believe all of them have involved cut down and rethreaded barrels (a few of these were Centurion Arms 11.5" barrels.. which were cut down from 12.5 by Monty).

Most of the time the device will thread on most of the way before require some torque to finish the journey, other times it will need a wrench to help move it on its way (after locking barrel into a vice) but this is the second one I've had that won't thread fully only the barrel even with some coercion (wrench).

I suppose I'll try a die first. I'd rather not buy all the tools as I haven't been spending as much time tinkering lately and I'm afraid it would sit there untouched after its maiden voyage.

[patrick sweeney]

I suppose I'll try a die first. I'd rather not buy all the tools as I haven't been spending as much time tinkering lately and I'm afraid it would sit there untouched after its maiden voyage.

That's the usual service life of many tools. When you need it, nothing else will do, but if you don't need it, it is an expensive and lightweight doorstop.

[nova3930]

That's the usual service life of many tools. When you need it, nothing else will do, but if you don't need it, it is an expensive and lightweight doorstop.

Irregularly used tools is what harbor freight was made for isn't it? :D

[patrick sweeney]

Good luck getting a 1/2-28 tap or die out of Harbor Freight.

They can be useful, but some things they just look at you with a puzzled expression.

[jwperry]

How far down the threads does it go before it starts binding?
Is it possible that muzzle device and barrel are threaded at different pitches?

[nova3930]

Good luck getting a 1/2-28 tap or die out of Harbor Freight.

They can be useful, but some things they just look at you with a puzzled expression.

You speak truth, but where harbor freight fails, Amazon prevails. :laugh:

If it something I use all the time I pay for quality, but if it's a one time use thing I'm all about the cheapies...

[buckjay]

How far down the threads does it go before it starts binding?
Is it possible that muzzle device and barrel are threaded at different pitches?

You can feel the extra resistance about 1/4" into the threads. It starts to really slow down just past half way mark and I don't really want to push it any further.

[jwperry]

You can feel the extra resistance about 1/4" into the threads. It starts to really slow down just past half way mark and I don't really want to push it any further.

Sounds like the muzzle device has way too much anodyzing(sp?) in it.
If you don't have that tap, I'd swing into an Autozone or Discount Autoparts and ask to borrow a 1/2"-28 tap and run it through in the parking lot. It will save you the cost if that isn't the issue, but it sounds like something is wrong at that end, especially if you have an A2 that will thread onto the barrel and a visual inspection doesn't show any flat spots on the threads of the barrel.

[patrick sweeney]

Don't guess, don't spend money until you have to, and don't jump into this.

Find someone at your gun club, or a buddy, who has a factory-threaded barrel. Try your muzzle device on his barrel. That will give you a big head's-up as to where the problem is.